Abstract
In charging argumentum ad hominem, we accuse someone of attacking the source of a claim. In charging argumentum ad verecundiam, we attack the source of a claim. This is reason for attending to "attacking the source." It is important to distinguish probabilistic reasons for doubting a claim and evidentiary reasons. Evidence that the source of a claim is likely to be wrong is not evidence against the claim. The tendency to overlook this is the essential feature of the ad hominem fallacy. This is relevant in assessing the view that someone who regards his thinking as made possible by Godless arrangements of matter largely determined by chance is, in taking this attitude, advancing a hypothesis which undermines his theorizing about the world or himself.